South Africa’s former President Nelson Mandela’s stay in a military hospital has extended into a fifth day, as the anti-apartheid icon receives treatment for a lung infection.

The 94-year-old leader is being treated at 1 Military Hospital near South Africa’s capital, Pretoria. President Jacob Zuma’s office has said Mandela is responding to the treatment.

In January 2011, Mandela was admitted to a Johannesburg hospital for what turned out to be an acute respiratory infection. He also contracted tuberculosis while in prison.

Mandela is revered for being a leader of the struggle against racist white rule in South Africa and for preaching reconciliation once he emerged from prison in 1990 after 27 years behind bars. He served one five-year term as president before retiring from public life.